(For the complete article, click through to the May 2019 digital edition.)
The demand from consumers for natural products—including cosmetics—continues to increase. Eco-friendly, organic and sustainable options are in the mainstream of this trend. Moreover, active phenolics derived from natural sources are playing an important role in the safety and efficacy of cosmetics.1
In relation, rice, or Oryza sativa cv. indica (Oryzeae), is well-known as the major staple in Asian cuisine. It has long been used in traditional Asian medicines as well as Italian remedies, including for aesthetic benefits for skin.
The profiles of the biological actives in rice differ during grain development and are particularly high during the flowering phase between 0-7 days of the development, during which the panicle, or cluster of branches, is still green. Flowering rice panicle was therefore explored, as described next, for applications as an eco-friendly, sustainable, safe and efficient active ingredient for cosmetics.2-4
Furthermore, beneficial integration between cosmetic manufacturers and the farmers who grow the active ingredient plants provides an opportunity to improve the local quality of life, giving would-be cosmetic consumers a path toward goodwill. The present work relates to rice farmed in Chiang Rai, the northernmost province in Thailand, located in the renowned Golden Triangle area. Home to majestic mountains and breathtaking waterfalls, this area is inhabited by farmers whose incomes heavily rely upon rice cultivation.
Materials and Methods
Rice panicle extract: The rice panicles of five different varieties cultivated in Chiang Rai were harvested; two glutinous rice varieties and three longer grain organic white rice. The harvested rice panicles were treated and prepared by a method developed to yield phenolic-rich extracts.2-4
Total phenolics content (TPC): The TPC of each extract was comparatively analyzed by Folin-Ciocalteu assay.2-4
Phenolics analysis: The content of the cosmetic active phenolics was analyzed by the validated ultra-performance liquid chromatography (UPLC) method;5 particularly gallic (GA), protocatechuic (PA), chlorogenic (ChA), caffeic (CA), syringic (SyA), p-coumaric (pCA), ferulic (FA), sinapic (SiA) and rosmarinic (RA) acids; as well as vanillin (V) and quercetin (Q).
In vitro antioxidant activity: The extracts were assessed for antioxidant activity in vitro by 2, 2'–azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing ability of plasma (FRAP) assays and compared with the standards.2-4
p-Coumaric and ferulic acids, along with 10 additional minor phenolics, were identified as the extract's major active constituents.
In vitro enzyme inhibitory effects: The inhibitory effect of the extracts against mushroom tyrosinase was assessed as per elastase and collagenase (see Figure 1).2-4
Properties and stability: The solubility of the extract was examined in different cosmetic vehicles, whose appearance and physicochemical properties were recorded prior to stability testing under accelerated conditions.2, 3
Activity in human skin fibroblasts: The extract safety profile was investigated, and antioxidant activity of the extract was analyzed in fibroblasts at the safe dose.5
Activity in B16F10 melanoma cells: The cytotoxicity of the extract in melanoma cells was examined. Inhibitory effects against melanogenesis, tyrosinase and tyrosinase related proteins-2 (TRP-2) were assessed at the safe extract concentration.5
Rice panicle cream development: A base and test cream containing (or not) the rice panicle extract, (see Formula 1) was developed and physicochemically evaluated. It stability also was tested by means of a centrifugation assay and seven heat-cool cycles.3, 5
Clinical evaluations: Finally, a study protocol following the guidelines of the Declaration of Helsinki and Tokyo was approved by the ethics committee of Mae Fah Luang University. Primary skin irritation tests were performed in 25 subjects by a single application, closed-patch test for 24 hr on the volar forearms of the subjects. Skin irritation severity was graded from 0-4 to calculate the Mean Irritation Index (MII). A MII < 0.2 was interpreted as non-irritating. The base and rice panicle creams were examined in parallel with 0.5% sodium lauryl sulfate (positive control) and water (the negative control).
A randomized, double-blind, placebo-controlled efficacy study was conducted in 24 healthy volunteers who applied the samples twice daily (morning and evening). The treated skin was evaluated for characteristics such as hydration levelsa, elasticityb, melanin and erythemac, and surface topographyd at the baseline and after 2, 4, 8 and 12 weeks of treatment.3, 5
Statistical analysis: The measured parameters were compared and analyzed using one sample t test and ANOVA test, with a significance level of p < 0.05 using softwaree.
Results: In vitro
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